Hydraulic system



Jan. EH, 1939. R. ELLIS 2,145,540

HYDRAULIC SYSTEM Filed 11%.. 16, 1931 3 Sheets-Shet 2 lZZ lay mm m v m mE w L 7 Jan. 31, 1939.

R. ELLIS 2,145,540

HYDRAULIC S Y5 TEM Filed Dec. 16, 1931 3 Sheets-Sheet 3 INVENTOR E. L. E/fi's ATTORNEY Patented Jan. 31, 1939 2,145,540

'"f ATES PATENT; Robert L. nun, Miami Beach, pplication December 16, 1931, Serial No. 581

14 Claims. (01. Gil-i) My invention relates to apparatus for supplymechanism used for controlling thepassag e ing liquid under pressure to hydraulic operating liquid under pressure to specific valves in pre mechanism and particularly to apparatus adaptdetermined timed relation, and I e 7, ed for use in combination with gas producing ap- Fig. 4 illustrates a modifl ation of a: portion ,5 paratus to actuate hydraulic'operating mechaof the apparatus illustrated in Big. 2. 1 '5 nism forone or a plurality of devices employed In the preferred embodiments illustratedlnthe therein, such as the valves for admitting steam drawings, my invention is shown as employed in to the apparatus, valves for purging the steam combination with gas making appa atus andthe and oil lines, devices for introducing and spreadpresent description will be confined to the em;

ing fuel, etc. bodiments oi the" invention illustrated, It "will 10 Heretofore the valves used in gas producing be understood, however, that the novel ieatures apparatus have been operated manually or by and improvements of my invention are susceppressure liquid supplied by a pump operating tible of use in combination with other types of continuously and=provided with a by-pass'and a apparatus, machines and operating mechanism l5 surge tank to apply liquid under pressure to wherein liquid under pressure is employed. Hence s hydraulically operated mechanism for the valves." the scope of the invent on t c ne the Manual operation is diflicult and is not dependembodiment thereof herein described. s able and the use of pumps and surge tanks re-' In the form of the invention illustrated in sults in a continued loss of air from the surge Figs. 1 toj3inclusive,gas makingapparatus of 2 0 tank, resulting in uneven pressure. Moreover, the back-run water gas typeis shown compris-. so

systems including pumps and associatedm'eching a generator *2, carburetor 4, superheater 5, anism are expensive to install and due to the and back-run pipe 8 which may be of any suite many moving parts, such systems require excesable construction. Operationbf the water gas sive costs for maintenance and repair. set involves numerous movingjparts actuated by In accordance with my invention hydraulic hydraul c cylindenm han smas I9! XfilIlPlQ'fl g5 apparatus is provided in which water or other stack valve I 0, back-run valve. and charging. liquid is passed back and forth repeatedly through machine 14 including spreader I 6, etc, Each oi; the hydraulic operating mechanism while consaid elements may be operated hydraulically by tinuously maintaining a supply or liquid under means of operating mechanism ll! of any suit,

pressure. The apparatus of this invention inable type. v 30 volves. a minimum of moving parts and is of In order to' supply liquid under pressure to simple and rugged construction. It is therefore the various'hydraulic operating mechanisms, inexpensive to construct and maintain. provide two tanks 20 and 22, each adapted to Among the objects of my invention are to' contain a body of liquid under Pressu e 1170.

provide a new and imp e sys em for supplyin which the liquid i c rged-to a pressure line as liquid under pressure to hydraulic operating 24 and to which liquid dischar ed .irom .hc Qp-.

mechanism, to reduce the cost of installation, crating mechanism is passed through a drain line operation and maintenance of hydraulic appa- 26 and returned to the other tan The tanks ratus and to provide automatic means operative 0 and 2 may be of any table construction in a continuous and dependable manner to 0pand preferably are each of suiiicient cia pacity to 40 erate hydraulic mechanism such as that emupply pre r liquid to erate h h d aulic ployed for operating the valves and other mechmechanism of a large gas plant for a period oi anism in gas making apparatus. hours, and in the case of a small gas plant each These and other objects'a'nd features of my tank may be of a capacity sullicient to supply 45, invention will appear from the following deall-of the pressure liquidrequired for operation scription thereof in which reference is made to over a period of a day or more. the accompanying-figures of the drawings illus- In order that, liquid may be supplied continue trating preferred embodiments of "my invention. ously under pressure to the pressure line 2.4, I

In the drawingsprovidesuitable check valves in the pres Fig-1 is a diagrammatic illustration of my line and drain line to permit liquid under g invention as applied to a water gas set of the sure to pass from whichever tank is under press back-run type. sure to the operating mechanism and thence Fig. ,2 is an enlarged view of a portion of the to the drain line and back to the other tank, apparatusillustrated in Fig. 1. As shown in Fi ,2, the; pressure line -24 -;isc one Fi a illustrates details :of con ru t on or nected to the tank 20 through t i as n w 55 ing an outwardly opening check valve 30 therein, and to the tank 22 through a pipe 32 having an outwardly opening check valve 34 therein. The drain line 26 is connected to the tank 20 through the pipe 36 and inwardly opening check'valve 38 to the T 40 in pipe 28. Similarly the drain line 26 is connected to the tank 22 through the pipe 42 and in-wardly'opening check valve 44 to the T 46 in the pipe 32. The check valves 30, 34, 38 and 44 are movable under pressure to allow liquid to pass from whichever tank is under pressure to the pressure line 24 and to allow liquid to return through drain line 26 to pass to whichever tank is under no pressure. In this way a continuous flow of liquid under pressure to the pressure line 24 is assured irrespective of which tank is supplying the liquid.

The sequence and timed relation of the hydraulic operating mechanism for the various valves and elements 01' the gas making apparatus is controlled by a device commonly referred to as a control nest, such as that illustrated in part'in Figs. 2 and 3. The control nest indicated at 48 in Fig. 1 is connected with each of the hydraulic operating mechanisms to which liquid-. under pressure is to be supplied. However, for simplicity of illustration only one hydreiplicoperating mechanism I8 and only one 'I'cont'rol nestvalve have been shown in the det ailed.portion of the control nest illustrated in shaft 56 at a constant speed. Cams 58 and 60 secured to the shaft 56 are provided for actuating theflvalve 62 by engaging the roller 64 secured to the valve stem 66. Only one set of cams and one valve are fully shown in Figs. 2 and 3, but it will be understood that as many sets of cams and Ir valves are'provi'ded as are necessary for operating 'the'variousvalves and elements of the gas making apparatus;-

valve stem 66 extends through packing gland 68 into the tubular chamber I0 and is prov vided with valve closures I2 and I4 which control the flow of liquid through the pipes I6 and III to a IldffIfOIIl" the cylinder of the operating mecha nisnri IB. In the position shown the liquid under pressure passes from header 41 in pressure line '-:24"through the channel 80 between the valve closures I2 and I4 to the" pipe I6 to force the piston 82 of the operating mechanism downwardly. Liquid below the piston 82 then passes through the pipe I8 to the channel 84, thence to theheader 49in drain line 26 and back to tank 22.

When the shaft 56 rotates to bring the cam 58 in contactwith roller 64, the valve stem is moved downwardly so that the valve closures I2 and I4 are moved into positions below the connections 'of the pipes I6 and I8 respectively with the cylinder I0. The direction of flow of the liquid is thereby reversed from that shown and the piston 82 is returned to the position illustrated in Fig.2.

With each movement of the piston of each operliquid in the cylinder is forced into the drain line 26 and back into the tank which is not at that time under pressure.

During the period when liquid is being discharged from the tank 20, fluid under pressure, such as steam, is supplied from any suitable source, such as steam line 86, and is admitted to the upper part of the tank through the pipe88 controlled by pressure valve 96. In passing liquid from the tank under pressure, for instance, tank 20, through the pressure line 24, control nest 48, operating mechanism I8 and drain line 26 to the tank 22, the level of liquid in the tank 20 continuously falls and the level of the liquid in tank 22 rises. Floats 92 and 94 are located in the tanks 20 and 22 respectively and the change in level of the liquid therein therefore causes the float 92 to move downwardly gradually until it reaches the position 92'. At the same time the float 94 rises as the level of the liquid in tank 22 rises until the float reaches the position 94. Float operated valves 96 and 98 are operatively connected with the floats 92 and 94 respectively by the arms I00 and are rotated thereby.

The operation of the valves 86 and 98 serves to actuate a control device to operate pressure valve 90 to cut off the supply of steam to the tank under pressure and admit steam to the tank which is not under pressure. When the level of liquid in tank 20 has fallen to that represented by the position 92 of the float, the valve 96 is operated automatically to connect the source of steam to the pipe I02 leading to the top of tank 22 and fluid under pressure is admitted to the tank 22 to discharge liquid therefrom. The tanks 20 and 22 are provided with exhaust valves I04 and I06 respectively, operable to close automatically when pressure is applied to the tanks so that the application of steam or other fluid under' pressure to either tank closes the exhaust valve associated therewith. The exhaust valves are opened by operation of the control device to relieve the pressure applied to the tank from which liquid has been discharged.

The control device by means of which pressure valve 90 and exhaust valves I04 and I06 are operated, comprises a cylinder IIIl within which a piston H2 is movable to operate the shaft II4 to which an arm II6 on the valve 90 is secured by the link H8. The opposite ends of the shaft I I4 carry cam members I20 movable into engagement with projections I22 on the exhaust valves I04 and I06. In-this way the pressure applied to a tank from which liquid has been discharged is relieved by the control device as the piston and shaft move to operate the pressure valve.

The piston of the control device is movable under pressure of fluid, such as water from a city water main, controlled by the operation of float operated valves 96 and 98. In the position of the float operated valves shown in Fig. 2 water passes from the pipe I24 to T I26 and pipe I28 to valve 98, thence through pipe I30 to the lefthand side of piston II2 incylinder IIO. Water from the right-hand side of the piston passes out of the cylinder through the pipe I32 to valve 96 and thence through pipe I34 to the T I36 and to sewer. The amount of water thus used is negligible since the control device is operated only when the liquid from one tank has been discharged and the pressure valve is reversed. When the float valves move from their full line to their dotted line positions, the positions of valves 96 and 98 are reversed so that water passes through pipe I24, T I26 and pipe I38 to valve 96 andthence'. through pipe I32 to'the right-' hand side of the piston I I2.' Water is then discharged from the cylinder 1 lfl'through the pipe I30 to valve 98 and thence through pipe I40 to the T I36 andtofsewer. The pipes I30 and I32 are each'provided with an adjustable valve I42 and a by-pass I44 communicating with the cylinder II 0 near the end thereof in position to be closed as the piston approaches the end of the cylinder. Thus when water is passed into the cylinder IIO through the pipe I30, the piston" after an initial slow movement which uncovers the by-pass I44 moves toward the right rapidly until the by-pass I Y the cylinder is covered. slowly through the remaining short portion of its stroke.

piston the pressure valve 90 is moved into posi- 20, but the cam with the exhaust valve I06 for tank 22. The piston then moves more slowlytoward the end of the cylinder until cam I20 actuates valve I06 to permit steam to escape from tank 22 to relieve the pressure thereon. The brief period of time between the operation of the pressure valve 90 and the operation of exhaust valve I 06 gives an opportunity for pressure to build up in tank 20 so that both tanks are momentarily under pressure, thus insuring a continuous supply of liquid under pressure to the pressure line 24 for actuating the hydraulic operating mechanism of the gas making apparatus.

When the valve 90 is operated to admit steam to the tank 22, the exhaust valve I04 of tank 20,

which is substantially emptied of liquid, is posi: tively operated to relieve the pressure applied to said tank and communicate with the atmosphere. The tank 22 then being under pressure and the tank 20 under no pressure, the check valves 30, 34, 38 and 44 in the piping leading to the pressure line and drain line, reverse auto matically under the influence of pressure on the liquid in tank 22 and liquid under pressure passes from the tank 22 to pressure line 24 and from drain line 26 back into tank 20. Thus the sys tem continuously suppliesliquid under pressure for operating the hydraulic mechanism for the valves, etc., whereas the liquid is conserved and passed back and forth from one tank to the other. Each of tanks 20 and 22 is provided with an over-flow valve I08 adapted to permit excess liquid to be discharge from the tank but operable to close under fluid pressure applied to the tank to prevent the escape ofsteam therefrom.

In the modified form of the apparatus shown in Fig. 4 the construction and operation of the tanks 20 and 22', pressure line 24', drain line 26 and fioat operated valves 96 and 98' are the same as that of the apparatus shown in Fig. 2. Steam or fluid under pressure is passed from the steam line 86' through pipes 88' and I02 to separate pressure valves I 50 and I52 associated with the tanks 20' and 22 respectively. The valves are similar instructureand therefore only one valve need bedescribed in full. Each valve is in the form'of a cylinder I54, open to the atmosphere at the outer end and provided with a slidable member I56 having closures I 58 and 160 thereon, The pipe 88 communicates with the cylinder at a point spaced from the open outer end thereof and the pipe I62 cornmunicates'wit-h the cylinder nearer the open end thereof; When the valve is in the position shown, -the"slidable member is in its extreme outer position and steam by the closure at the right-hand end of The piston then moves During the rapid movementof the from the drain line to the detail as embodied illustrated in the drawings, I intend the foregoing not to limit the same.

is admitted to the tank 20'. In this position the end of the cylinder is closed to the atmosphere I58. When water in the tank falls to the level shown in tank 22, the valves 96' and 90 operate to admit water into the left-hand end of cylinder IIlI' causing piston-I I2 to'move to the left. Shaft H4 is thus moved to throw the operating arm' I64 of valve and'move the slidable member I56 position with the closure I56, closing the end of the cylinder and with the pipe I02 communicating with the pipe I66 of tank 22 to admit steam under pressurether'eto. As the piston I I2 moves to the left, the shaft II4 moves into engagement with the operating arm I 64 of valve I50 I retracting the slidable member and moving clo-' cut off the supply. of and allow steam from sure I58 into position to steam from the pipe 88' the tank 20 to escape to the atmosphere through the end of the cylinder, thus relieving the pres+ sure on the liquid in tank apparatus one valve is operated to admit steam to the associated chamber before the pressure is relieved on the other chamber. Therefore it is unnecessary to provide a by-pass for the liquid flowing .to cylinder H0, such as that employed in the construction shown in Fig. 2.

'I'heoperatlon of theiorms of apparatus heretofore described will appear from the foregoing description thereof. In each instance liquid is passed from a tank under pressure line to a control nest. flows to whichever of the various hydraulically operated mechanisms isto be operated, dependtank is raised. When a predetermined amount of liquid has-been discharged from the tank under pressure, i. -e., when the level of the liquid has fallen to a certain point, the float operated valves operate to admit water to the control device to operate the same and cause steam or other fluid under pressure tobe admitted to the tank which previously was under no pressure and which now contains a large amount of liquid, and to relieve the pressure on the tank from which the liquid was previously discharged. The check valves in the pressure and drain lines operate automatically to direct the liquid under pressure to the pressure line and return liquid tank which now is under no pressure.

Although I have described my invention in in the forms of apparatus description to be illustrative of my invention and It will therefore be un derstood that'numerous changes and modifications may be made in the apparatus without departing from the spirit and scope of the invention, For-example, while an apparatus involving two tanks-has been described, it will be understoodthat'more than two tanks may be employed,

if desired. Further, while the tanks are shown and described as separate and detached, it will be understood that they may be combined in a single casing or housing which is divided by I52 to the left outwardly into 20. In this form of the one or more partitions into two or more compartments or tanks.

I claim:

L-Apparatus for supplying liquid under pressure to hydraulically operated mechanism comprising a plurality of tanks each adapted to con tain liquid, means for supplying fluid under pressure' to one of said tanks to cause discharge of liquid therefrom while permitting return of the liquid discharged into another of said tanks,

and means controlled by the level of liquid in said tanks to interrupt the supply of pressure fluid to the-tank to which pressure fluid has been suppliedfand-to supply the pressure fluid to another ofsaid tanks.

.2. Apparatus for supplying liquid under pressure to hydraulically operated mechanism comprisingv a plurality of tanks adapted to contain liquid under pressure, means for conducting liquid from a tank under pressure to said hydraulically operated mechanism and thence to another of said tanks whereby the level of liquid in said tanks is changed, a source of fluid under pressure, a float in each of said tanks and means connected to said floats operable when the level of the liquid in a tank under pressure has fallen to a predetermined level to admit fluid from said source to another tank and to relieve the pressure applied to that tank from which liquid has been discharged. 7

j 3. Apparatus for supplying liquid under pressure to hydraulically operated mechanism comprising two tanks adapted to contain a body of liquid under pressure, a pressure line and a drain line connected to each of said tanks and tosaid hydraulically operated mechanism, check valves in said lines constructed and arranged to allow liquid to flow from whichever tank is under pressure. to the hydraulically operated mechanism and thence to the other tank, a source of fluid under pressure, a pressure valve movableto admit fluid from said source to either of said tanks, exhaust valves for relieving pressure applied to said tanks, a control device for operating said pressure valve and said exhaust valves, and actuating mechanism operated in response to the .discharge of a predetermined amount of liquid from the tank which is under pressure to operate said control device and reverse said pressure and exhaust valves to admit fluid under pressure to that tank which previously was under no pressure, and to relieve the pressure on that tank which previously was under pressure.

4. Apparatus for supplying liquid under pressure to hydraulically operated mechanism comprising two tanks adapted to contain a body of liquid under pressure, a pressure line and a drain line connected to each of said tanks and to said hydraulically operated mechanism, check valves insaid lines constructed and arranged to allow liquid to flow from whichever tank is under pressure to the hydraulically operated mechanism and thence to the other tank whereby the level of the liquid in said tanks is changed, a source of fluid under pressure, a pressure valve movable to admit fluid from said source to either of said tanks, exhaust valves for relieving pressure ,applied to said tanks, a control device for operating said pressure valve and said exhaust valves, a float in each of said tanks, mechanism rendered operative by the joint movement of the float in one tank to a predetermined upper level and the movement of the float in the other'tank to a predetermined lower level to actuate said control device to-reverse said pressure and exhaust valves whereby fluid under pressure is applied to that tank in which the float is at a predetermined upper level and the pressure applied to the other tank is relieved through said exhaust valve.

5. Apparatus adapted for supplying liquid under pressure to the operating mechanism of each of a plurality of hydraulically operated valves of a gas producing apparatus comprising two tanks adapted to contain a body of liquid under pressure, a pressure line and a drain line connected to each of said tanks and to said hydraulically operated mechanism, check valves in said lines constructed and arranged to allow liquid to flow from whichever tank is under pressure to the hydraulically operated mechanism and thence to the other tank, a source of fluid under pressure, a pressure valve movable to admit fluid from said source to either of said tanks, exhaust valves for relieving pressure applied to said tanks, a control device for operating said pressure valve and said exhaust valves provided with a cylinder, a piston movable in said cylinder, members operated by movement of said piston to actuate said pressure valve and said exhaust valves to admit fluid under pressure to that tank to whichliquid previously flowed from said oper ating mechanism and to relieve the pressure applied to that tank previously under pressure, a float in each of said tanks, a float operated valve associated with each of said tanks and operated by the float therein, and pipes connecting said float operated valves to said cylinder, said float operated valves being movable to admit fluid under pressure to said cylinder and to permit fluid to be discharged from said cylinder.

6. Apparatus for supplying liquid under pressure to hydraulically operated mechanism of gas making apparatus comprising a plurality of hydraulically operated elements, a plurality of tanks adapted to contain liquid under pressure, means for passing liquid from a tank under pressure to each of said hydraulically operated elements and thence to another tank, a control device for controlling the passage of liquid to and from said elements, a source of fluid under pressure, and means operable when a predetermined amount of liquid has been discharged from a tank under pressure to admit fluid under pressure to another tank and relieve the pressure applied to the tank from which liquid has been discharged.

7. Apparatus adapted for supplying liquid under pressure to the operating mechanism of each 0! a plurality of hydraulically operated valves of a gas producingapparatus comprising two tanks adaptedto contain a body of liquid under pressure, a pressure line and a drain line connected to each of said tanks and to said hydraulically operated mechanism, check valves in said lines constructed and arranged to, allow liq-' uid to flow from whichever tank is under pressure to the hydraulically operated mechanism and thence to the other tank, a source of fluid under pressure, a pressure valve movable to admit fluid from said source to either of said tanks, exhaust valves for relieving pressure applied to said tanks,

a control device for operating said pressure valve and said exhaust valves provided with a cylinder, a piston movable in said cylinder, elements movable in response to movement of said piston to first operate said pressure valve to admit pressure to that tank to. which liquid previously flowed from said operating mechanism and thereafter to operate the exhaust valve for that tank previously under pressure, a float in each of said tanks.

a float operated valve associated with each of said tanks and operatively connected to a float therein, pipes connecting said valves to said cylinder, a second source" of liquid under pressure communicating with said valves, and means connected to said pipes to control the flow of liquid therethrough to regulate the movement of said piston whereby said pressure valve is operated prior to the operation of said exhaust valves.

8. Apparatus for supplying liquid under pressure to hydraulically operated mechanism for operating the valves of Water gas making apparatus comprising, hydraulic apparatus for supplying liquid under pressureto the operating mechanism for said valves comprising two tanks adapted to contain a body of liquid under pressure, a pressure line and a drain line connected to each of said tanks and to the hydraulic operating mechanism for said valves, check valves in said lines to cause fluid to flow from whichever tank is under pressure to said hydraulic operating mechanism and then to the other tank, whereby the level of liquid in said tanks is changed, a control nest communicating with said pressure line and drain line to control the passage of liquid under pressure from said pressure line to the hydraulic operating mechanism for said valves and to control the flow of liquid from said hydraulic operating mechanism to said drain line, a source of fluid under pressure, a pressure valve movable to admit fluid from said source to either of said tanks, exhaust valves for relieving the' pressure applied to each of said tanks, a control device movable to operate said pressure valve and said exhaust valves, and float operated mechanism controlling the operation of said control device to reverse said pressure and exhaust valves and cause fluid from said source to be admitted to that tank in which liquid is at a higher level and to relieve the pressure applied to that tank in which the liquid is at a lower level.

9. Apparatus comprising in combination, a hydraulic mechanism operable in a plurality of directions by liquid under pressure, means for supplying liquid under pressure to said hydraulic mechanism to operate thesame in each of said directions, said supplying means cdmprising a plurality of tanks adapted to contain liquid under pressure, means for conducting liquid from a tank under pressure to said hydraulic mechanism and thence to another of said tanks, said conducting, means including valve means operable to establish a path of flow for the liquid from the tank under pressure to said hydraulic means and a path of flow from said hydraulic mechanism to another of said tanks to operate said hydraulic mechanism in one direction, said valve being also operable to establish a second path of flow from said tank under pressure to said hydraulic mechanism and a second-path of flow from said hydraulic mechanism to another ofsaid tanks to operate the mechanism in another direction, and means operable when a predetermined amount of liquid has been discharged from a tank under pressure to admit fluid under pressure from a source thereof to another tank and to relieve the pressure applied to the tank from which liquid has been discharged.

10. Apparatus comprising in combination, a cylinder and a hydraulically operated piston therein, means for supplying liquid under pressure to either side of said piston to operate the same in either of two directions, said supplying means comprising a plurality of tanks adapted to contain liquid under pressure, means for conducting liquid from a tank under pressure to either side of said piston to operate the same in either direction, and thence to another of said tanks, at source of fluid under pressure and means operable when a predetermined amount of liquid has been discharged from the tank under pressure to admit fluid under pressure from said source to another tank and to relieve the pressure applied to the tank from which liquid has been discharged.

11. Apparatus comprising in combination, hydraulic mechanism operable by liquid under pressure in a plurality of directions, a plurality of tanks adapted to contain liquid under pressure, means for conducting liquid from a tank under pressure to said hydraulically operated mechanism to operate said mechanism in any of said directions and thence to another of said tanks, a source of fluid under pressure, and means operable when a predetermined amount of liquid has been discharged from the tank under pressure to admit fluid under pressure from said source to another tank and to relieve the pressure applied to the tank from which liquid has been discharged.

12. Apparatus comprising in combination, hydraulic mechanism operable by liquid under pressure in a plurality of directions, a plurality of tanks each adapted to contain liquid under pressure, a source of fluid under pressure, a valve operable to admit fluid from said source to. one of said tanks, means for passing liquid from a tank under pressure to said hydraulically operated mechanism to operate said mechanism in any of said directions and thence to another of said tanks, and means actuated when a predetermined amount of liquid has been discharged from the tank under pressure to ,operate said valve to admit fluid from said source to another tank.

13. Apparatus for supplying liquid under pressure to hydraulically operated mechanism comprising a plurality of tanks, each adapted to contain liquid, means for supplying fluid under pressure to one of said tanks to cause discharge of liquid therefrom while permitting return 'of the liquid discharged into another of said tanks, a valve individual to each of said tanks, said valves being movable to interrupt the supply of pressure fluid to the tank to which pressure fluid has been supplied and to supply the pressure fluid to another of said tanks, and means controlled by the level of liquid in said tanks to actuate said valves.

14. Apparatus for supplying liquid under pressure to hydraulically operated mechanism comprising a plurality of tanks adapted to contain liquid under pressure, means for conducting liquid from; a tank'under pressure to said hydraulically operated mechanism and thence to another of said tanks whereby the level of liquidin said tanks is changed, a source of fluid under pressure, a valve individual to each of said tanks, said valves being movable to interrupt the supply of pressure fluid to the tank to which pressure fluid has been supplied and to supply the pressure fluid to another of said tanks, a float in each of said tanks and means connected to said floats operable when the level of the liquid in a tank under pressure has fallen to a predetermined level to actuate said valves to relieve the pressure applied to the tank from which liquid has been discharged and to admit pressure fluid from said source to another of said tanks.

ROBERT L. ELLIS. 

